We have fabricated blend films comprising 6,13-bis(triisopropylsilylethynyl) pentacene (TIPS pentacene) as a semiconducting small molecule and poly(methyl methacrylate) (PMMA) as an insulating polymer by electrostatic spray deposition (ESD). A thin film (5 nm) of molybdenum trioxide (MoO3) was evaporated on the entirety of the active layer surface. Then, we found that the off-state current in OFETs using the TIPS pentacene/PMMA blend films apparently increased. This result probably indicates the formation of a conductive surface channel due to the MoO3 deposition. In this study, we performed morphological and chemical analyses. In consequence, we found that only Mo atoms (not together with O atoms) penetrated into TIPS pentacene and oxidation of Mo to MoOx could enhance charge transfer between neighboring TIPS pentacene molecules. Furthermore, this study demonstrated that the off-state current could be modulated by changing the ambient condition, such as relative humidity.

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